Gas turbine system



Oct. l5, 1946. v R. c. ALLEN 2,409,176

GAS TURBINE SYSTEM Filed April 10, 1942 Patenteci ct. 15, 1946 STATES PATENT OFFICE GAS TURBINE SYSTEM Application April 10, 1942, Serial No. 438,367

Claims.

This invention relates generally to vehicle propulsion and more particularly to propulsive jet forming power units for aircraft and other types of vehicles.

Jet propulsion uni-ts heretofore proposed embodying a gas turbine and a compressor driven thereby are rendered impractical primarily because of their extremely low operating efficiencies, andit is therefore the main object of this invention to provide in a propulsive jet forming power unit of this type, an improved correlation of features affording a practical degree of operating efficiency. In accordance with this invention, a practical degree of operating efficiency is obtained by combining the elements of the unit (1) for operation with the highest permissible turbine inlet temperature and a conformingly high compression ratio, thereby developing a maximum of excess power (i. e., power in addition to that required by the compressor) under conditions effecting maximum thermal elciency and, (2) for eiiciently utilizing the excess power developed by the turbine to increase the propulsive effort of the propelling jet or jets.

Another object of this invention is to provide an improved jet propulsion unit embodying a propelling jet forming nozzle structure and a gas turbine driven compressor combination correlated in a novel manner to produce a large mass of jet forming gas yand thereby a high propulsive effort under conditions effecting maximum thermal eiciency.

Still another object of this invention is to provide an improved jet propulsion unit embodying a gas turbine driven compressor combination correlated to operate with maximum thermal eiciency, to utilize the excess power developed by the turbine to materially increase the mass of jet forming gas, and to divide the large mass of jet forming gas between the turbine and a surrounding passage eifective to provide concentric propelling jets affording a high propulsive effort.

4Still another object of this invention is to provide in a jet propulsion unit an improved correlation of features comprising uid compressing means, a gas turbine drivingly connected with the fluid compressing means, means forming a passage connecting the discharge of the fluid compressing means with the inlet to the turbine, means for highly heating the uid fiowing through the passage, propelling jet forming nozzle means, and means severally connecting the exhaust of the turbine and the passage with the nozzle means.

A further object of this invention is to prov, embodying the invention.

Referring to the drawing, it is seen that `a propulsion jet forming power unit embodying the invention may include an axial compressor I having a forwardly facing inlet 2, an axial flow gas turbine 3 axially spaced from and drivingly connected with the discharge end of the compressor I by means of a hollow shaft 4 disposed within a tube B connecting the housings of the adjacent turbine and compressor rotor bearings 1 and 8, respectively, an inner shell member 9 which surrounds the tube 6, an outer shell member II having its rear portion surrounding and forming with the casing of the turbine 3 an annular passage I2 and having its forward portion surroundingand forming with the inner shell 9 of an annular passage i3 which connects the discharge end of the compressor I with the inlet to the turbine 3 and with the passage l2, and a rearwardly flaring annular mixing and combustion tube I4 which is supported Within the passage I3 by means of circumferential series of radially extending struts designated I6 and II and which has disposed therein a plurality of fuel nozzles I8.

The forward end of the compressor rotor is supported in a bearing I9 which is in turn supported by the forward end of the compressor casing by means of brackets or the like 2l. The 'rear compressor bearing 8 is supported in a similar manner by brackets 22. The forward end of the compressor rotor is provided with a shaft portion which extends beyond the bearing I9 and carries a gear 23 meshed with a worm (not shown) onthe transversely extending shaft 24 mounted for rotation in the gear box 26. 'I'he exposed end of the shaft 24 is splined as indicated for connection with a starting prime mover (not shown) The forward end of the compressor rotor, gear 23, gear box 2B, and the exposed end of shaft 24 are enclosed in a casing member 21 which may be removably secured to the forward end of the compressor rotor and the struts 28 in order to afford ready access to the parts en- 3 closed therein. The forward end of the compressor casing and the member 2l coact and form therebetween the annular inlet 2 for the compressor I.

The forward bearing 1 of the turbine 3 is supported within thc inner shell 9 by means of brackets or the like 29 which are formed integral with or secured to the forward end of the turbine easing. The rear end of the turbine rotor is supported by a bearing 3I which is inturn supported in a similar manner to the bearing 'I by means of brackets 32. The inner rear end of the turbine rotor and the bearing 3| are enclosed in a casing member 33 which may be removably secured to the turbine casing and the struts 34 in order to afford ready access to the parts enclosed therein. The casing member 33 coacts with the outer rear portion of the turbine casing and forms therewith an annular nozzle portion 36 through which the turbine exhausts and which is surrounded by the annular converging nozzle portion 31 formed between the rear end portion of the outer shell II and the outer rear end portion of the turbine casing. The rear end of the outer shell extends beyond the rear end of the turbine 3 and forms with the casing member 33 a rearwardly directed nozzle 38 into which the nozzle portions 36 and 31 discharge. The outer front end of the turbine casing is braced within the outer shell II by means of a circumferential series of struts 39 and is extended forwardly a material distance to provide in effect an annular, dividing means 40 acting to apportion the fluid flowing rearward through the passage I3 between the inlet to the turbine 3 and the passage I2.

Stated differently, the outer shell II coacts (1) with the inner shell 9 to form therebetween a high temperature motive fluid passage I3 connected with the discharge of the compressor I, and (2) with the turbine casing to form therewith a surrounding passage I2 which connects the passage I3 with the nozzle portion 31, thereby providing in effect means severally connecting the nozzle 31 (also nozzle portion 38) and the turbine inlet with the high temperature motive fluid passage. In other words, the inner and outer shells coact with each other and with the cornpressor and turbine and form (l) a fluid heating passage means fthe passage I3 which includes the mixing and combustion tube I4) connecting the discharge of the compressor with the turbine inlet. and f2) means comprising the passage I2, nozzle portion 31 and the nozzle portion 36 severally connecting the exhaust of the turbine and the heated passage with the nozzle portion 38.

In operation, the air discharged from the compressor I enters the passage I3 in which it is highly heated, preferably by the combustion of fuel therein as indicated, and the resulting mixture of combustion gases and excess air is apportioned between the turbine inlet and the passage I2. The passage I2 terminates in a converging nozzle portion 31 designed to maintain the desired pressure at the turbine inlet. 'VIhe turbine exhausts through the annular nozzle portion 36 and the fluid in the passage I2 flows through the surrounding nozzle 31 and is combined with the exhaust from the turbine 3 in the continuing nozzle portion 38. If a greater propulsive effect is desired, the velocity' of the gas in the nozzle portion 38 can be readily increased by employing one or more auxiliary fuel burning nozzles 4I as indicated, since the gases contain sufficient excess air to support combustion. The use of auxiliary fuel nozzles is desirable for accelerating the unit and the nozzle structure can be readily cooled to withstand the higher temperature thus produced, since it has no moving parts.

When considering the compressor, combustion chamber and gas turbine combination as an cxccss power developing unit, it must be borne in mind that within practical temperature limits the higher the turbine inlet temperature the higher the thermal efhciency and that the higher the turbine inlet temperature the higher the compression ratio for maximum thermal ellleiency. Consequently, it should be obvious that in order to obtain maximum thermal efficiency for such a combination, it is necessary to operate under conditions effecting the highest permissible turbine inlet temperature and a conv formingly high compression ratio, thereby developing a maximum of excess power, and that in order to obtain a high propulsive effort, it is necessary to efficiently utilize the excess power developed by the turbine to increase the propulsive effort of the propelling jet or jets. This result is accomplished in the unit shown and described `for purposes of illustration by employing a compressor designed to utilize all of the excess power developed by the turbine in compressing additional air and by employing a dividing means operative to conduct all of the additional air; i. e., air in excess of that required for operating the turbine under conditions effecting maximum thermal efficiency, directly to the jet forming nozzle portion 38, thereby materially increasing (l) the mass of compressed, and in this case highly heated, air available for the production of a propulsive jet or jets, and (2) the propulsive effort.

The invention is applicable to all forms of jet propelling power units embodying said combinations and it should therefore be understood that it is not intended to limit the invention to the exact manner of combining and operating the elements of the unit `as herein shown and described, as various modifications within the scope of the appended claims may occur to persons skilled in the art.

It is claimed and desired to secure by Letters Patent:

1. A jet propulsion unit comprising fluid compressing means having a forwardly facing inlet, a gas turbine axially spaced from and drivingly connected with the discharge end of said fluid compressing means, an axially extending conduitV means interposed between and connecting the discharge end of said compressing means with the inlet to said turbine, means for highly heating the fluid flowing through said conduit means, propelling jet forming nozzle means, and means severally connecting the exhaust of said turbine and the passage formed by said conduit means with said nozzle means.

2. A jet propulsion unit comprising fluid compressing means having a forwardly facing inlet, a gas turbine axially spaced from and drivingly connected with the discharge end of said fluid compressing means, means forming an axially extending combustion chamber interposed between and connecting the discharge end of said compressing means with the inlet to said turbine. propelling jet forming nozzle means, and means severally connecting the exhaust of said turbine and said combustion chamber with said nozzle means.

3. A jet propulsion unit comprising fluid compressing means having a forwardly facing inlet. a gas turbine axially spaced from and drivingly connected with the discharge end of said fluid compressing means, means forming a coaxial passage connecting the discharge of said iluid compressing means with the inletl to said turbine, means for highly heating the fluid owing through said passage, propelling jet forming nozzle means, and means severally connecting the exhaust of said turbine and said passage with said nozzle means.

4. A jet propulsion unit comprising fluid compressing means having a forwardly facing inlet, a gas turbine axially spaced from and drivingly connected with the discharge end of said iiuid compressing means, means forming a coaxial passage connecting the discharge of said fluid compressing means with the inlet to said turbine, combustion apparatus in said passage. propelling jet forming nozzle means, and means severally connecting the exhaust of said turbine and the turbine inlet end of said passage with said nozzle means.

5. A jet propulsion unit comprising an axial compressor having a forwardly facing inlet, an axial flow lgas turbine axially spaced from and drivingly connected with the discharge end of said compressor coaxial, rearwardly directed propeiling jet forming nozzle means connected with the exhaust of said turbine, means'forming a coaxial annular combuston chamber connected with the discharge of said compressor, and means forming inner and outer coaxial annular passages severally connecting the inlet to said. turbine and said nozzle f means with said combustion chamber.

ROBERT C. ALLEN. 

